The penetration power of the roots into the soil has been studied in relati
on to field crops but not to container media. In this work the mechanical i
mpedance of sand, perlite, peat, coir and commercial mixtures were evaluate
d: Fafard no 2, Fafard 2P, Jiffy 7 and Oasis. Dry and saturated samples wer
e analyzed under four levels of compactation. Jiffy 7 and Oasis were analyz
ed only in the original density of the manufactured products. The impedance
was measured by a metal probe and a digital micropenetrometer. The penetra
tion pressure is correlated to the level of compactation of the media, with
significant interaction between compactation and moisture level.